Preparation of oximes



United States Patent PREPARATION OF OXIMES Harry Welz and Aloys Gilt'ges, Krefeld, Germany, as-

signors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany N Drawing. Application June 25, 1952, Serial No. 295,556

Claims priority, application Germany June 28, 1951 12 Claims. (Cl. 260-566) It is known to produce oximes by the reduction of alkali salts of primary or secondary nitro compounds of the aliphatic or cycloaliphatic series with nascent hydrogen. In that method an aqueous solution of an alkali metal salt of the nitro compound is introduced into the acid to which there has previously been added a metal for the production of hydrogen. This has the disadvantage that a considerable part of the nitro compound is reduced to the amine instead of the oxime and the yield of oxime is correspondingly reduced.

According to the present invention the reduction of the salts of primary or secondary nitro compounds of the aliphatic or cycloaliphatic series to the amine is largely repressed and the yield of the oxime correspondingly increased by adding to an acid a mixture of a metal, preferably in a finely dispersed form, with a dilution, i. e. an aqueous solution or suspension of an alkali metal or an alkaline earth metal salt of nitro alkanes or cycloalkanes, the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom i. e. of primary or secondary nitro alkanes or cyclo alkanes.

The above mentioned alkali metal or alkaline earth metal salts of the said nitro alkanes or cyclo alkanes e. g. the sodium, potassium, lithium, calcium, barium or strontium salts can be easily obtained, in a manner known per se, by reacting the nitro alkanes or cyclo alkanes with the corresponding alkali metal or alkaline earth metal hydroxides.

As nitro alkanes the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom can be used for example aliphatic mononitro alkanes such as nitroethane, 2-chloro-l-nitroethane, l-nitropropane, Z-chloro-l-nitropropane, 2-nitropropane, l-chloro- 2-nitropropane, l-nitrobutane, Z-nitrobutane, l-nitropentane, 2-nitropentane, 2-nitrohexane, l-nitrononane, lnitro-2,7-dimethyloctane, l-nitroundecane and the mononitro alkanes obtainable by nitration of the alkanes of the Fischer-Tropsch synthesis, cycloaliphatic mononitroalkanes such as nitrocyclohexane, 2-nitro-l-methylcyclohexane, S-nitro-l-methylcyclohexane, l-nitrodecahydlronaphthalene and Z-nitrodecahydronaphthalene, polynitro alkanes such as 1,1-dinitroethane, 1,2-dinitroethane, 1,1- dinitropropane, 1,2-dinitropropane, 1,1-dinitrobutane, 2,3- dinitrobutane, 1,4-dinitrobutane, 1,1-dinitropentane, 1,5- dinitropentane, 2,3-dinitro-2-methylbutane and the polynitro alkanes obtainable by nitration of the alkalines of the Fischer-Tropsch synthesis, finally cycloaliphatic polynitro alkanes such as 1,2-dinitrocyclohexane, 1,3-dinitrocyclohexane and 1,4-dinitrocyclohexane.

The preferred acids for the production of nascent hydrogen are sulphuric acid, hydrochloric acid, nitric acid or acetic acid.

Suitable metals are such which are known to be used for producing nascent hydrogen for example, beryllium, magnesium, aluminium, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron. The metal which is to be added to the dilution of the salt of the nitro com- 2,721,880 Patented Oct. 25, 1955 pound may be used in a finely dispersed form. We have found that the best yields are obtained, when using the metal of a particle size less than 0.2 mm. especially less than 0.06 mm. The metal is advantageously applied in an excess of the theoretically required amount.

In general it is advisable to perform the conversion at a pH below 3, and particularly below 2.

Generally the reaction may be performed in the temperature range above the freezing point and below the decomposition point of the reaction components the best results being obtained in the temperature range about 0 to about 50 and particularly of about 10 to about 30.

The following examples are given for the purpose of illustrating the invention:

Example 1 A mixture of a solution of 129 g. of nitrocyclohexane in 450 grams of a 10% caustic soda solution with grams of finely ground zinc dust is added drop by drop to grams of a 5% hydrochloric acid in the course of half an hour while stirring vigorously. By adding hydrochloric acid during the conversion, a pH below 2 of the reaction solution is ensured. The reaction temperature is kept at about 10 C. by cooling with a freezing mixture. After the conversion is completed, the reaction mixture is neutralized whereupon the main part of the oxime precipitates. The precipitate is filtered off and dried. The filtrate still contains small amounts of dissolved cyclohexanone oxime, cyclohexanone and cyclohexanol which may be recovered by extraction with benzene and separation by vacuum distillation. After the extraction, the filtrate is made alkaline, and the cyclohexylamine is dissolved out by extraction with benzene. The yields are: 84 grams of cyclohexanone oxime (75% of the theoretical), 1 gram of cyclohexanone, 7 grams of cyclohexanol and 13 grams of cyclohexylamine.

If, according to the prior art, zinc dust had been first added to the hydrochloric acid in a known manner, and the solution of nitrocyclohexane in caustic soda solution were then added to the acid, the yields would be as follows: 25 grams of cyclohexanone oxime (22% of the theoretical), 8 grams of cyclohexanone and 73 grams of cyclohexylamine.

Example 2 A mixture of a solution of 75 grams of nitroethane in 450 grams of a 10% caustic soda solution with 36 grams of finely ground magnesium powder is added drop by drop to 100 grams of a 3% sulphuric acid in the course of half an hour, while stirring vigorously. By adding sulphuric acid a pH of 1 is maintained during the conversion. The reaction temperature is kept at 20 C. by cooling. After the conversion is completed, the reaction mixture is neutralized, and extracted with benzene. After the benzene has been distilled off, 41 grams of acetaldoxime (70% of the theoretical) is obtained. The ethylamine dissolved as sulphate is liberated from the solution by a solution of caustic soda, and dissolved out with benzene (yield 9 grams).

If, according to the prior art, magnesium powder had been first added to sulphuric acid, and the solution of nitroethane in caustic soda solution were then added to the acid, the yields would be as follows: 18 grams of acetaldoxime (30% of the theoretical) and 28 grams of ethylamine.

Example 3 A mixture of a solution of 129 grams of nitrocyclohexane in 450 g. of a 10% caustic soda solution with -76 grams of finely ground iron with a particle size of chloric acid is added in such a manner that the pH of the reaction solution remains below 1. The reaction temperature is held at about +10 C. by cooling with a freezing mixture. When the reaction is finished the reaction mixture is regulated at a pH of about 3 and the precipitated oxime then is filtered off and dried. The mixture of cyclohexanone oxime, cyclohexanone and cyclohexanol, dissolved in the filtrate, is then obtained by extracting with benzol. Then the extract is distilled in vacuo. The yields are: 63 grams of cyclohexanone oxime (56% of the theoretical), 4 grams of cyclohexanone, and 23 grams of cyclohexanol.

When using iron dust with a particle size of less than 0.06 mm. the yield of cyclohexanone oxime is increased to 83 grams (74% of the theoretical). The yields of cyclohexanone and cyclohexanol then are 1 gram and 9 grams respectively.

We claim:

1. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a dilution of material selected from the group consisting of the alkali metal and the alkaline earth metal salts of nitro alkanes and nitrocyclo alkanes the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

2. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a solution of an alkali metal salt of a nitro alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

3. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a solution of an alkali metal salt of a mononitro alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

4. The process for the production of acetaldehyde oxime, which comprises adding to a 3% sulphuric acid solution a mixture of finely ground magnesium powder with a solution of the sodium salt of nitroethane.

5. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a suspension of an alkaline earth metal salt of a nitro alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

6. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a suspension of an alkaline earth metal salt of a mononitro alkane the nitro group of which is connected with a carbon atom at least one hydrogen atom.

7. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a solution of an alkali metal salt of a nitro cyclo alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

8. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a solution of an alkali metal salt of a mononitro cyclo alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

9. The process for the production of cyclohexanone oxime, which comprises adding to a 5% hydrochloric acid solution a mixture of finely ground zinc dust with a solution of the sodium salt of nitrocyclohexane.

10. The process for the production of cyclohexanone oxime, which comprises adding to a 5% hydrochloric acid solution a mixture of finely ground iron with a particle size of less than 0.06 mm. with a solution of the sodium salt of nitrocyclohexane.

11. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a suspension of an alkaline earth metal salt of a nitrocyclo alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

12. The process for the production of oximes by reduction of salts of organic nitro compounds by nascent hydrogen, which comprises adding to an acid a mixture of a metal of the group consisting of beryllium, magnesium, aluminum, zinc, cadmium, tin, chromium, manganese, nickel, cobalt and iron, in a finely dispersed form, with a suspension of an alkaline earth metal salt of a mononitrocyclo alkane the nitro group of which is connected with a carbon atom carrying at least one hydrogen atom.

References Cited in the file of this patent UNITED STATES PATENTS Sussie Mar. 4, 1941 OTHER REFERENCES 

1. THE PROCESS FOR THE PRODUCTION OF OXIMES BY REDUCTION OF SALTS OF ORGANIC NITRO COMPOUNDS BY NASCENT HYDROGEN, WHICH COMPRISES ADDING TO AN ACID A MIXTURE OF A METAL OF THE GROUP CONSISTING OF BERYLLIUM, MAGNESIUM, ALUMINUM, ZINC, CADMIUM, TIN, CHROMIUM, MANGANESE, NICKEL, COBALT AND IRON, IN A FINELY DISPERSED FORM, WITH A DILUTION OF MATERIAL SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METAL AND THE ALKALINE EARTH METAL SALTS OF NITRO ALKANES AND NITROCYCLO ALKANES THE NITRO GROUP OF WHICH IS CONNECTED WITH A CARBON ATOM CARRYING AT LEAST ONE HYDROGEN ATOM. 